DisabledCommand.cs

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// Copyright (c) 2014 Silicon Studio Corp. (http://siliconstudio.co.jp)
// This file is distributed under GPL v3. See LICENSE.md for details.
using System;

namespace SiliconStudio.Presentation.Commands
{
    /// <summary>
    /// This class represents a command that is always disabled and does nothing when executed.
    /// </summary>
    /// <remarks>This class is a singleton, you can access to the instance via the static property <see cref="Instance"/>.</remarks>
    public sealed class DisabledCommand : ICommandBase
    {
        static DisabledCommand()
        {
            Instance = new DisabledCommand();
        }

        /// <summary>
        /// Gets a singleton instance of the <see cref="DisabledCommand"/>
        /// </summary>
        public static DisabledCommand Instance { get; private set; }

        /// <summary>
        /// Initializes a new instance of the <see cref="DisabledCommand"/> class.
        /// </summary>
        private DisabledCommand()
        {
        }

        /// <inheritdoc/>
        public bool IsEnabled { get { return false; } set { if (value == false) throw new InvalidOperationException("The IsEnabled property of the DisabledCommand cannot be modified"); } }

        /// <inheritdoc/>
        public event EventHandler CanExecuteChanged
        {
            add { }
            remove { }
        }
        
        /// <inheritdoc/>
        public bool CanExecute(object parameter)
        {
            return false;
        }

        /// <inheritdoc/>
        public void Execute(object parameter)
        {
            throw new InvalidOperationException("The DisabledCommand cannot be executed.");
        }

        /// <inheritdoc/>
        public void Execute()
        {
            throw new InvalidOperationException("The DisabledCommand cannot be executed.");
        }
    }
}